In recent years, an analysis method using a microchip called “μ-TAS (μ-Total Analysis System)” or “Lab on a chip,” which performs a chemical analysis, by applying the micromachine technology thereto, receives attention.
Such an analysis system, which uses such a microchip (hereinafter referred to as a microchip analysis system), aims at performing an entire process of an analysis including mixture, reaction, separation, extraction, and detection of a reagent in a fine flow path formed on a small substrate by the micromachine production technology. For example, in the medical field, such a system is used for an analysis of blood and an analysis of biomolecules, such as ultratrace protein and nucleic acid etc.
Especially, when human blood is analyzed, using the microchip analysis system, there are a variety of advantages, that is, (1) since the quantity of the blood (sample) needed for analysis and examination is small, a toll on its body can be reduced, (2) since the quantity of the reagent which is mixed with the blood and used therefor is small, analysis cost thereof can be reduced, (3) since the apparatus itself can be configured so as to be small, the analyze can be easily performed. Because of these advantages developments are increasing.
Generally, in such a microchip analysis system, for example, absorptiometry is a method used for measuring the concentration of a component of an object to be detected in the sample liquid. A clinical laboratory test apparatus using such absorptiometry, which is disclosed in Japanese Patent Application Publication No. 2007-No. 322208, is known.
FIG. 12 is a schematic cross-sectional view of an internal structure of a measurement unit of such a clinical examination analysis apparatus. The clinical laboratory test apparatus is equipped with a casing (not shown), wherein the measurement unit, a light source, and a light receiving unit are provided in the casing, as shown in FIG. 12. The measurement unit 100 has a measurement room 101, as shown in FIG. 12, and a rotation body 102, which is a cylinder with a bottom arranged in the measurement room 101. A driving shaft 103B arranged to penetrate the center of a lower face of the rotation body 102, extending in up and down directions and connected to a centrifugal motor 103A. The rotation body 102 is rotated by driving the centrifugal motor 103A. A rotation drive mechanism 103 is made up of the above-mentioned centrifugal motor 103A, the driving shaft 103B, and an encoder 103C, which is described below.
A gear 107 for a direction change, whose outer diameter is smaller than the radius of the rotation body 102, is provided in a bottom of the rotation body 102, wherein the gear 107 for a direction change is provided on the rotation body 102, and is rotatably supported by an axis thereof with respect to the axis parallel to the center of the rotational axis. A chip holding unit 106 for holding a microchip is provided on the gear 107 for a direction change. In addition, in FIG. 12, in order to maintain the rotation balance of the rotation body 102 in a proper state, another chip holding unit 106 that has the same structure as the above mentioned chip holding unit 106 is provided in the opposite side so that the rotational-axis center is located between these chip holding units 106.
An opening 101A for light guide and an aperture portion 102A, which guide light entering through a reflection mirror 132 from a light source 131 into a microchip measurement area (area where sample liquid is placed) in a state where the microchip is held by the chip holding unit 106 in a lower part of the measurement room 101, are formed in the rotation body 102 and the gear 107 for a direction change, to which the chip holding unit 106 are provided, respectively. A light receiving unit 133 receives light, which passes through the microchip measurement area. An optical fiber 134 guides the received light. An opening 101B for example is formed in an upper part of the measurement room 101 so as to place the light receiving unit 133 and the optical fiber 134.
It is necessary to perform an absorbance determination of a sample liquid in the microchip measurement area in a state where rotation of the rotation body 102 is stopped, and to guide the light from the above-mentioned light source 131 in the microchip measurement area. Therefore, it is necessary to precisely control the stop position of the rotation body 102. For this reason, the encoder 103C is connected to the centrifugal motor 103A, which rotates and drives the rotation body 102, and the stop position of the rotation body 102 is controlled based on a signal from the encoder 103C.
Moreover, a sheet heater 115 for keeping the temperature in a measurement room 101 constant (for example, 37 degrees Celsius) at the time of analysis and examination is formed in an area, which is part of an upper and lower faces of the measurement room 101. The heater 115 is controlled, based on the temperature detected by a temperature measuring unit 116 such as a thermistor, so that the temperature in the measurement room 101 becomes constant.
Moreover, in order to adjust the direction of the microchip held by the chip holding unit 106, the measurement unit 100 has a chip direction change mechanism 110, which has a drive mechanism separated from the rotation drive mechanism 103 for driving and rotating the rotation body. This chip direction change mechanism 110 comprises, for example, a driving side gear 113 that is provided rotatably with respect to the driving shaft 103B of the centrifugal motor 103A through a ball bearing 112 and that meshes with the gear 107 for a direction change, and a motor 111 for a chip direction change, which is a drive source for rotating and driving the driving side gear 113. The driving side gear 113 is rotated by driving the above-mentioned motor 111 for a chip direction change, so that the gear 107 for a direction change, and the chip holding unit 106 are rotated, whereby, the direction (direction with respect to the rotational-axis center of the rotation body 102) of the microchip can be changed.
For example, an analysis processing of the sample liquid is performed by the clinical laboratory test apparatus as set forth below. The rotation body 102, on which the microchip holding the sample (blood) is placed, is rotated, and a separation processing, which carries out centrifugal separation of the sample, is performed using a centrifugal force, and the sample liquid obtained by the separation processing is weighed. Further, a mixing and reaction treatment, which mixes and reacts the sample liquid to be measured and a reagent with each other, and a pretreatment operation including a processing for sending the liquid to be measured, which is obtained by the mixing and reaction treatment, to the measurement area, are performed.
Subsequently, the light receiving unit 133 receives light, which is guided from the light source 131 into the measurement area of the microchip, in a state where rotation of the rotation body 102 is stopped. Thereby, the amount of optical absorption is measured from the liquid to be measured, which is in the measurement area.